The present invention relates generally to fluid pressure regulators, and more specifically to pressure regulating valves whose set point pressures can be electrically modulated.
Applications have existed for some time for pressure regulating valves capable of regulating to either of two electrically selected pressures, or to any pressure within an operating pressure range. In general, these applications have been somewhat specialized, and the required volumes relatively small, thus providing little incentive for exploring nontraditional designs or technologies. Typically, traditional designs for two stage or modulating pressure regulator valves have employed a solenoid actuator to control the force supplied by a regulator spring.
A pressure regulating valve application which has begun to receive increasing interest is in connection with fuel gas valves for small furnaces, such as those used in single family residences. Certain U.S. furnace manufacturers have developed high efficiency furnace designs which rely on two stages of furnace operation. When heat is first called for and under moderate heat requirements, the furnace is fired at a low to moderate rate. If firing at that rate does not provide the heat output required for the existing conditions, firing is stepped up to a higher rate.
Along with the increasing demand for in such furnaces has come increasing interest in an improved two stage or modulating fuel gas valve design which avoids certain disadvantages of the existing solenoid actuator based designs. The desired improvements include smaller size, quieter operation, simpler construction with fewer moving parts, and lower cost. Conventional solenoid actuators have been relatively bulky, and tend to be noisy in operation. Two sources of operating noise include abrupt movement of the solenoid plunger, with attendant vibration when it reaches the limits of its travel, and buzzing or humming if the solenoid is energized with alternating current.
In Europe and Japan there is also increasing interest in higher efficiency fuel gas fired furnaces. The preferred design approach in those areas appears to be modulation of the firing level, in contrast to a two stage approach. However, either design approach requires a gas valve capable of regulating to an electrically selected pressure.
The applicant has devised an improved design for a two stage or modulating pressure regulating valve based on unique technology by which the short comings of prior art designs can be avoided. In particular the applicant's design is compact in size, quiet in operation, has a minimum number of moving parts, and can be produced at low cost.